#include <bits/stdc++.h>
#define int long long

using namespace std;

void solve () {
    int mx, my;
    cin >> mx >> my;

    string s;
    cin >> s;

    int x = 0, y = 0;
    int u = 0, d = 0, l = 0, r = 0;
    for (auto c : s) {
        if (c == 'U') {
            u ++;
            y ++;
        } else if (c == 'D') {
            d ++;
            y --;
        } else if (c == 'L') {
            l ++;
            x --;
        } else {
            r ++;
            x ++;
        }
    }

    if (mx == x && my == y) {
        cout << "Impossible\n";
        return;
    }
    if (mx == 0 && my == 0) {
        cout << "Impossible\n";
        return;
    }

    vector <int> p (4);
    iota (p.begin (), p.end (), 0);
    do {
        int x = 0, y = 0;
        bool ok = true;
        for (int i = 0; i < 4; i ++) {
            if (p[i] == 0) {
                if (mx == x && my >= y && my <= y + u) {
                    ok = false;
                    break;
                }
                y += u;
            } else if (p[i] == 1) {
                if (mx == x && my <= y && my >= y - d) {
                    ok = false;
                    break;
                }
                y -= d;
            } else if (p[i] == 2) {
                if (my == y && mx <= x && mx >= x - l) {
                    ok = false;
                    break;
                }
                x -= l;
            } else {
                if (my == y && mx >= x && mx <= x + r) {
                    ok = false;
                    break;
                }
                x += r;
            }
        }
        if (ok) {
            for (int i = 0; i < 4; i ++) {
                if (p[i] == 0) {
                    cout << string (u, 'U');
                } else if (p[i] == 1) {
                    cout << string (d, 'D');
                } else if (p[i] == 2) {
                    cout << string (l, 'L');
                } else {
                    cout << string (r, 'R');
                }
            }
            cout << '\n';
            return;
        }
    } while (next_permutation (p.begin (), p.end ()));

    cout << "Impossible\n";
}

signed main () {
    ios::sync_with_stdio (false);
    cin.tie (nullptr);

    int T = 1;
    cin >> T;

    while (T --) {
        solve ();
    }

    return 0;
}